1. Field of the Invention
This invention relates generally to a trench shielding unit for securing the sidewalls of a trench or excavation from cave-in, and particularly to a trench shielding unit having adjustable vertical panels to improve access and protection of workers and to underground utilities traversing the excavation area.
2. Description of the Prior Art
In construction, it is often required to excavate underground utilities such as water, gas or sewer lines, pipes, cables, drainage conduit and/or culverts, by digging ditches, trenches and the like of various lengths and depth. Trench shielding units are often used to protect workers and property from cave-ins or landslides by safeguarding against shifts or the collapse of the walls of the excavation. In fact, Occupational Safety and Health Administration (OSHA) regulations require that any excavation over five feet deep be properly shielded to prevent cave-ins or to protect workers inside an excavation in the event of a cave-in.
By contrast, shoring is often used as a more permanent landscaping structure to prevent the sidewall of earthen formations from moving or collapsing, so as not to damage nearby building foundations, shorelines, walkways, bridges, roadways or other architectural structures. More particularly, the positive supporting of a sidewall in this field is called “shoring” while the protection against collapse is called “shielding.”
As previously stated, the current practice in the construction industry is to use a trench shielding unit inside an excavation to protect workers, equipment and underground structures. These units are generally open between opposing walls and at the bottom so that digging can continue while the unit is in place. Of course, the top of the unit is also open for easy access by workers and machinery for removal of dirt or other debris, as well as pipe, equipment and/or tools.
Generally, the structure of a trench unit includes opposing side panels to hold the excavation in place. Additionally, the trench unit has a plurality of bars or beams, more commonly referred to as spreader bars, that transverse the lateral width of the trench unit to hold opposing side panels in spaced relationship. Upon completion of the excavation work, the trench unit is either removed or abandoned in place, and the excavation site is filled.
There are a variety of trench units in use, such as, for example, U.S. Pat. No. Re. 30,185 to Griswold which shows a typical trench shield assembly having protective sidewalls maintained in space relation by spreader bars. Further, U.S. Pat. No. 5,310,290 to Viollaz shows another such shielding unit having legs which telescopically adjust to provide clearance about a structure traversing the trench. Further yet, the shoring unit shown in U.S. Pat. No. 7,021,868 to Farrag et al. describes a lightweight unit that can be assembled above ground and lowered into the excavation to accommodate access to utility pipelines traversing the excavation area, in addition to protecting the worker from sidewall collapse. None of these systems, however, is able to accommodate easily and quickly unplanned obstructions or unanticipated traversing structures passing through the trench.
This invention improves the current field of trenching units by providing opposing sidewalls having a plurality of interengaging panels that are easily adjustable vertically without sacrificing structural strength and reliability of the unit.